[Andrew Eastman]

Andrew Eastman  asked the Naked Scientists:
   
Hello Naked Scientists

My name is Andrew, and I am from the USA, but I am currently living in Indonesia.   I very much enjoy your podcast and listen to it as often as I can.

So I have always been very interested in evolution, and I feel I have quite a good understanding of it, but there is one aspect of it that recently occurred to me that I didn't very well understand yet.  

I understand how complex organs which make up an organism evolve into what they are, but I am curious about how some animal instincts evolve into what they are.  More specifically, I am interested in understanding how instincts for building complex structures evolve?

The types of structures that I am referring to are those such as beaver lodges, bee hives, bird nests, etc. What makes some animals evolve this instinct for building homes or egg shelters for themselves and why many other animals need not build anything at all.

I do not understand how an incurred instinct for building complex structures occurs.   I envision the evolution of an animals dwelling as evolving in the same way the animal itself evolves, but I just don't understand how this works.  

Is there any way of knowing what the evolution of something like a beaver lodge was (I'm guessing it's not in the fossil record)? And, in general I just don't understand exactly how instinct  originates and perpetuates itself  in  the evolutionary  process.   Can you guys help me to understand all this?
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Andrew

What do you think?

[_Stefan_]

It may help you to think of complex instinctive behaviors as organs, because they evolve by the same mechanisms. Behaviors are produced by the brain, and are executed by other parts of the body. An organism is built by genes, and the genes can influence the organism's behaviour via the brain. Genes that build an organism that produces behaviors that have neutral or positive effects on its reproductive success (in a particular environment), are more likely to be transmitted to subsequent generations. They are then subject to further modifications and selection as the behaviors they influence are optimised. In this way, simple behaviors, like simple tissues and organs and other traits, can become more complex over evolutionary time.

Richard Dawkins discusses this topic in great detail in his book The Extended Phenotype, which I highly recommend to you.

I hope this helps.